DE69809787T2 - ASSEMBLY METHOD FOR SEMICONDUCTOR COMPONENTS ON A PCB - Google Patents

Description

SUBJECT OF THE INVENTION

The present invention relates to a method of mounting a semiconductor element on a circuit board, which is used for electrically connecting protruding electrodes, i.e., solder bumps on the semiconductor element to electrodes on the circuit board, and further relates to a semiconductor device having a semiconductor element mounted on the circuit board according to the method.

STATE OF THE ART

US Patent 4,661,192 discloses in the published description a method for forming or producing solder bumps on a semiconductor element by ball bonding or by ball contacting and a method for bonding or contacting the semiconductor element. These known methods are explained below.

In Fig. 25, a high voltage of several thousand volts is applied from a discharge electrode (torch) 17 to a front end 16a of a gold wire 16 extending from a front end of a capillary 15. While a discharge current flows between the torch 17 and the front end 16a of the wire, the wire 16 is heated to a high temperature at its front end 16a and then melted, thereby forming a gold ball 18 as shown in Fig. 26. The ball 18 is attached to an electrode 3a of a semiconductor element 3 through the capillary 15, forming a lower bump portion 19 as shown in Fig. 27. Thereafter, the capillary 15 is pulled up as shown in Fig. 28 and the capillary 15 is moved in a loop over the lower solder bump section 19 so that the wire 16 adheres firmly to the lower solder bump section 19. The wire is then severed. In this way, a solder bump 20 is formed.

A semiconductor element 3 having the solder bumps 20 formed in the above-mentioned manner is pressed against a stage 14 having a flat surface as shown in Fig. 29. This flattens the front end portions of the solder bumps 20. Then, as shown in Fig. 30, the semiconductor element 3 having the flattened solder bumps 20 is brought into contact with a conductive adhesive 6 applied on a stage 5 to transfer the conductive adhesive 6 to the flattened solder bumps 20. In Fig. 31, the semiconductor element 3 having the solder bumps 20 to which the conductive adhesive 6 has been transferred is aligned and fixed to electrodes 2 on a circuit board 1, whereby the semiconductor element is electrically connected to the circuit board 1.

As explained above, in the prior art, the semiconductor element 3 and the circuit board 1 are bonded to each other only by the conductive adhesive 6 transferred to the solder bumps 20 of the semiconductor element 3. Therefore, the bonding between the semiconductor element 3 and the circuit board 1 has only a bonding strength of a portion at the front ends of the solder bumps 20 of the semiconductor element 3, and the conductive adhesive 6 exhibits a strength as small as 1 to 2.0 g at each bonded portion, since only a small amount of the conductive adhesive 6 is used to reduce the volume resistivity. These defects therefore lead to the fact that the contacted parts break as a result of a bend or deformation of the circuit board 1 or a load or stress when the conductive adhesive 6 hardens or sets, that a connection resistance value increases and that a loosening of the contact on the contacted parts occurs.

U.S. Patent 5,210,938 discloses a method of assembling an electronic element assembly on a circuit board, wherein an electrode formed on the electronic element assembly and a conductor pattern formed on the circuit board to face the electrode are provided. A thermosetting resin sheet containing particles that shrink when heat is applied and disposed between the electronic element assembly and the circuit board is cured and shrinks.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a method for mounting a semiconductor element on a circuit board in which connection reliability and connection strength in contacting between the semiconductor element and the circuit board are improved and a connection resistance value is stabilized at a low level, and further to provide a semiconductor device having a semiconductor element mounted on a circuit board by the method.

To achieve the above object, according to a first aspect of the present invention, there is provided a method for mounting a semiconductor element on a circuit board, which includes the following steps:

applying an insulating adhesive having a shrinkage property upon setting to at least each opposing surface of the circuit board and the semiconductor element which are opposed to each other;

aligning the circuit board and the semiconductor element so that an electrode on the circuit board corresponds to a protruding electrode on the semiconductor element;

Bonding the mating surfaces of the circuit board and the semiconductor element by the insulating adhesive; and

Curing the insulating adhesive so that the electrode on the circuit board and the protruding electrode on the semiconductor element ment are electrically connected to each other by the shrinkage of the insulating adhesive so that the semiconductor element and the circuit board are fixed in a connected state;

before applying the insulating adhesive, applying an insulating resin for protecting an electrode on the semiconductor element to the mating surface of the semiconductor element except for the portion of the protruding electrode which is connected to the electrode on the circuit board, wherein after setting of the insulating resin, the insulating adhesive is applied to at least each of the mating surfaces.

A semiconductor device according to a second aspect of the present invention comprises a semiconductor element mounted on a circuit board according to the above-described mounting method according to the first aspect.

According to the mounting method for a semiconductor element on a circuit board according to the first aspect and the semiconductor device according to the second aspect, the semiconductor element and the circuit board are bonded to each other using the insulating adhesive and are therefore firmly bonded compared with the prior art, and the bonding is achieved only through the protruding electrode of the semiconductor element and the electrode of the circuit board. Therefore, the bonding resistance value at the protruding electrode of the semiconductor element and the electrode of the circuit board is reduced and less changed, while the bonding strength is high, thereby achieving highly reliable bonding.

SHORT DESCRIPTION OF THE DRAWINGS

These and other aspects and features of the present invention will become more apparent from the following description in conjunction with the preferred embodiments thereof with reference to the accompanying drawing figures. In this:

Fig. 1 is a sectional view showing the structure of a semiconductor device in an embodiment of the present invention;

Fig. 2 is a schematic diagram showing a step of a manufacturing process of the semiconductor device shown in Fig. 1, particularly a state in which a conductive adhesive is transferred to protruding electrodes of a semiconductor element;

Fig. 3 is a schematic diagram showing a step of the manufacturing process of the semiconductor device shown in Fig. 1, particularly a state in which an insulating adhesive is transferred to a circuit board;

Fig. 4 is a sectional view of a modified example of the semiconductor device shown in Fig. 1;

Fig. 5 is a sectional view of another modified example of the semiconductor device shown in Fig. 1;

Fig. 6 is a sectional view of a still further modified example of the semiconductor device shown in Fig. 1;

Fig. 7 is a schematic diagram showing a state in which a part of the semiconductor element in the semiconductor device shown in Fig. 1 is removed;

Fig. 8 is a schematic diagram showing a step of the manufacturing process in a modified example of the semiconductor device shown in Fig. 1;

Fig. 9 is a schematic representation of a step of the manufacturing process of the modified example of the semiconductor device shown in Fig. 1, in particular a step subsequent to the representation of Fig. 8;

Fig. 10 is a schematic representation of a step of the manufacturing process of the modified example of the semiconductor device shown in Fig. 1 tion, in particular a step subsequent to the representation of Fig. 9;

Fig. 11 is a schematic representation of a step of the manufacturing process of the modified example of the semiconductor device shown in Fig. 1, in particular a step subsequent to the representation of Fig. 10.

Fig. 12 is a schematic representation of a step of the manufacturing process of the modified example of the semiconductor device shown in Fig. 1, in particular a step subsequent to the representation of Fig. 11;

Fig. 13 is a sectional view of the modified example of the semiconductor device shown in Fig. 1;

Fig. 14 is a schematic diagram showing a state in which a sealing resin is injected into the semiconductor device shown in Fig. 1;

Fig. 15 is a schematic diagram showing the structure of an apparatus for injecting the sealing resin into the semiconductor device shown in Fig. 1;

Fig. 16 is a schematic diagram showing a state in which the sealing resin has been injected into the semiconductor device shown in Fig. 1;

Fig. 17 is a sectional view of the semiconductor device shown in Fig. 1 with the sealing resin having been injected, the semiconductor device being coated with a heat-radiating resin;

Fig. 18 is a sectional view of the semiconductor device shown in Fig. 1 in a state where a second sealing resin is injected thereinto;

Fig. 19 is a sectional view of the semiconductor device shown in Fig. 1 in a state where the second sealing resin is injected therein;

Fig. 20 is a flowchart showing an operation of a method for mounting a semiconductor element on a circuit board according to an embodiment of the present invention;

Fig. 21 is a plan view showing an arrangement of a rectangular insulating adhesive when the sealing resin is injected into the semiconductor device shown in Fig. 1 in one direction;

Fig. 22 is a plan view showing an arrangement of an elliptical insulating adhesive when the sealing resin is injected into the semiconductor device shown in Fig. 1 in one direction;

Fig. 23 is a sectional view of the semiconductor device of the embodiment in another structure without using a conductive adhesive;

Fig. 24 is a sectional view of the semiconductor device of the embodiment having a different structure using a spherical semiconductor element;

Fig. 25 is a schematic representation of a step of a method for producing a protruding electrode on an electrode of a semiconductor element, particularly showing a front end part of a capillary;

Fig. 26 is a schematic diagram showing a step of the method for forming the protruding electrode on the electrode of the semiconductor element, particularly showing a state in which a ball is formed at the front end of the capillary;

Fig. 27 is a schematic representation of a step of the method for producing the protruding electrode on the electrode of the semi conductor element, particularly showing a state in which the ball of Fig. 26 is pressed or pressed onto the electrode on the semiconductor element;

Fig. 28 is a schematic diagram showing a step of the method for producing the protruding electrode on the electrode of the semiconductor element, particularly showing a state in which the protruding electrode is formed on the electrode of the semiconductor element;

Fig. 29 is a schematic diagram showing a step of the method for forming the protruding electrode on the electrode of the semiconductor element, particularly showing a state in which the protruding electrodes have been made uniform in height;

Fig. 30 is a schematic diagram showing a step of the method for producing the protruding electrode on the electrode of the semiconductor element, particularly showing a state in which a conductive adhesive is transferred to the protruding electrodes;

Fig. 31 is a schematic diagram of a prior art semiconductor device.

BEST MODE FOR CARRYING OUT THE INVENTION

A method of mounting a semiconductor element on a circuit board according to a preferred embodiment of the present invention and a semiconductor device having a semiconductor element mounted on a circuit board by the method will be described below with reference to the drawing figures in which like components are designated by like reference numerals.

Fig. 1 shows a semiconductor device 100 in which a semiconductor element 103 is mounted on a circuit board 101 according to an assembly method in the preferred embodiment. The assembly method for producing the semiconductor device 100 is explained below.

Similarly to the conventional semiconductor element explained with reference to Figs. 25 to 29, a protruding electrode 104 is formed as a bump on an electrode 103a of the semiconductor element 103. The protruding electrodes 104 are pressed against a flat surface of a stage so that the front end portions of the protruding electrodes are flattened and at the same time are made equal in height as viewed from a surface of the semiconductor element 103. The protruding electrodes 104 are preferably made of Au, Ni, Al, Cu or a solder material by plating or by known ball bonding using a wire, which has been explained above. The forming method is not limited to the above.

As shown in Fig. 2 and in a step 1 in Fig. 20 (the step is indicated by "S" in the figure), each front end portion of the protruding electrodes 104 of the semiconductor element 103 is brought into contact with a conductive adhesive 106 applied to the flat surface of the stage, thereby transferring the conductive adhesive 106 to the front end portions. The conductive adhesive 106 may be made of any kind of filler material having conductive properties, such as silver, gold and the like, but is not limited to these materials.

On the other hand, as shown in Fig. 3 and in a step 2 in Fig. 20, in manufacturing the semiconductor device 100 according to the present embodiment, a thermosetting insulating adhesive 107 is applied to a counter surface 101a facing the semiconductor element 103 at a location such that the adhesive does not come into contact with the electrodes 102 to be connected to the protruding electrodes 104. In particular, the insulating adhesive 107 may be a such adhesives as an epoxy series resin, a silicone series resin, a polyimide series resin, etc., as long as the adhesive shrinks and hardens or sets due to heat. As will be explained below, the insulating adhesive 107 is set in a range of 60 to 200°C, preferably at 120°C in the case of the epoxy series resin for 15 minutes to 2 hours, preferably for 1 hour, and shrinks in the same process as the conductive adhesive 106 of the protruding electrodes 104. Due to the need for the insulating adhesive 107 on the circuit board 101 to adhere to a mating surface 103b of the semiconductor element 103 to thereby bond the mating surfaces 101a and 103b to each other when the semiconductor element 103 is arranged on the circuit board 101, the insulating adhesive 107 should be shaped like a protrusion on the circuit board 101 as shown in Fig. 3 when the insulating adhesive 107 is in a liquid state. For this reason, the insulating adhesive 107 has a viscosity of 4 to 300 Pas, preferably 30 Pas when it is liquid.

In the description of the embodiment, the semiconductor element 103 to which the insulating adhesive 107 is applied or adhered is exemplified by a chip, but the invention is not limited to this form, so that the semiconductor element may be a wafer before it is cut into a chip.

An example of physical properties of the insulating adhesive 107 formed of an epoxy series resin is explained below. The insulating adhesive 107 sets at a heat of 120°C for 30 minutes. The thermal expansion coefficient is 29 x 10-6/°C, the elastic modulus is 10.5 GPa, the glass transition point is 113°C, the bonding strength is 88.26 N, and the setting stress is 882.6 x 10-6 Pa.

The setting stress applied to the semiconductor element 103 when the insulating adhesive 107 sets and shrinks involves the risk of damaging the semiconductor element 103. Although the setting stress varies in accordance with the thickness and size of the semiconductor element 103 varies with the material and width of the wire, with the thickness, size and material of the circuit board 101, the setting stress within 392.3 x 10⁶ to 1176.8 x 10⁶ Pa never damages the semiconductor element when the semiconductor element is made of 0.4 mm thick silicon of 10 mm square and the circuit board is made of 0.8 mm thick glass epoxy resin. In other words, when the insulating adhesive 107 used acts with the setting stress as described above on the semiconductor element 103 and the circuit board 101 during setting and shrinkage, the damage to the semiconductor element 103 and the circuit board 101 can be avoided.

In step 3 of Fig. 20, the protruding electrodes 104 of the semiconductor element 103 are aligned on the electrodes 102 of the circuit board 101 and subsequently bonded to the electrodes 102 on the circuit board 101 by the conductive adhesive 106. Following the alignment, the interposed insulating adhesive 107 bonds the mating surface 101a of the circuit board 101 to the mating surface 103b of the semiconductor element 103 between the semiconductor element 103 and the circuit board 101.

Subsequently, in step 4, which is referred to as a parallel setting process of Fig. 20, the semiconductor element 103 and the circuit board 101, i.e., the conductive adhesive 106 and the insulating adhesive 107, are set or hardened in the same process by heating and setting the insulating adhesive 107 and the conductive adhesive 106 in a curing furnace or by a heat tool having a heater that heats at least the semiconductor element 103 or the circuit board 101. As a result, the semiconductor device 100 shown in Fig. 1 is obtained. At the same time, the circuit board 101 and the semiconductor element 103 are not temporarily fixed to each other but permanently bonded to each other by setting the conductive adhesive 106 and the insulating adhesive 107.

A heating temperature in the curing oven is 120°C ± 10°C in the embodiment where an epoxy series resin adhesive is used. The conductive adhesive 106 and the insulating adhesive 107 are cured under the same conditions.

In the step 4, the insulating adhesive 107 is set so that it sets and shrinks before the conductive adhesive 106. The reason for setting or adjusting the timing in this way is that if the conductive adhesive 106 sets in a state where the protruding electrodes 104 and the electrodes 102 on the circuit board 101 are not contacted with each other, the damaged contacted state after the insulating adhesive 107 sets and shrinks is irreparable. The setting is carried out in a time sequence in which, for example, the insulating adhesive 107 sets and shrinks in 25 minutes and the conductive adhesive 106 sets within 40 minutes at a setting temperature of 100ºC, or the insulating adhesive 107 sets and shrinks in 20 minutes and the conductive adhesive 106 sets in 35 minutes at a setting temperature of 120ºC, or the insulating adhesive 107 sets and shrinks in 10 minutes and the conductive adhesive 106 sets in 20 minutes at a setting temperature of 150ºC.

In order to set and shrink the insulating adhesive before the conductive adhesive 106 at the above-mentioned timing and, further, to securely contact the protruding electrodes 104 with the electrodes 102 on the circuit board 101 by the insulating adhesive 107 that has been set and shrunk beforehand without causing damage such as cracks and the like to the semiconductor element 103, the insulating adhesive 107 having the above-mentioned physical properties is used. In order to further ensure a shift in the timing of setting, the insulating adhesive 107 is set to have a gelling time and a setting time that are earlier than those of the conductive adhesive 106. Furthermore, the insulating adhesive 107 is set to set at a lower temperature so as not to damage the semiconductor element 103 by its setting and shrinking. A difference in the gelling time and setting time between the insulating adhesive 107 and the conductive adhesive 106 is necessary due to a difference in the components. That is, the insulating adhesive 107 as an adhesive component contained in the insulating adhesive 107 is set while the conductive adhesive 106 is dried and solidified when a solvent component such as BCA (butyl carbitol acetate) contained in the conductive adhesive 106 evaporates. The presence/absence of the solvent component is a reason for the difference in the gelation time and setting time.

The setting stress applied to the semiconductor element 103 and the circuit board 101, i.e., the internal stress, changes according to a setting temperature, for example, it is 490.3 × 10⁶ Pa at 100°C for 30 minutes, 882.6 × 10⁶ Pa at 120°C for 30 minutes, and 1,520.0 × 10⁶ Pa at 150°C for 15 minutes. Therefore, not only the shifting of the timing of setting is required, but the setting stress should be 392.3 × 10⁶ to 1,176.8 × 10⁶ Pa as mentioned above.

Since the semiconductor element 103 and the circuit board 101 are bonded together by the insulating adhesive 107 and the conductive adhesive 106, the bonding strength between the circuit board 101 and the semiconductor element 103 is increased due to setting and shrinkage of the insulating adhesive 107 as compared with the prior art despite the stress applied to the bonded portion between the protruding electrodes 104 and the electrodes 102 of the circuit board 101 due to the difference in thermal expansion coefficients of the circuit board 101 and the semiconductor element 103 and due to warpage of the circuit board 101. As a result, a connection resistance between the protruding electrodes 104 and the electrodes 102 of the circuit board 101 is reduced and less changed, while at the same time the semiconductor element 103 and the circuit board 101 are contacted stably and with high reliability and with a large connection strength.

Although in the above description the insulating adhesive 107 is applied to the circuit board 101 to simplify the manufacturing process, the insulating adhesive 107 may be applied to the mating surface 103b of the semiconductor element 103 or to both the mating surfaces 101a and 103b of the circuit board 101 and the semiconductor element 103.

Moreover, although the insulating adhesive 107 is applied at only one point between the semiconductor element 103 and the circuit board 101 as shown in Fig. 1, the present invention is not limited to this, and the insulating adhesive 107 may be applied at a plurality of points as in the semiconductor devices 115, 116 shown in Figs. 5 and 6 with an increase in the area of the semiconductor element 103. When the insulating adhesive 107 is applied at two or more points, the amount of the insulating adhesive 107 applied at one time is reduced so that variations in the application amount are reduced, thereby making it possible to apply a constant amount of the insulating adhesive 107. The insulating adhesive 107 is prevented from splashing onto the electrodes 102 of the circuit board 101 when the semiconductor element 103 is mounted on the circuit board 101.

When the semiconductor element 103 and the circuit board 101 are bonded together as shown in Figs. 1, 5 and 6, the following effects occur when the insulating adhesive 107 is applied so that it does not adhere to any of the electrodes 103a of the semiconductor element 103 and the electrodes 102 of the circuit board 101. In the case where the semiconductor element 103 is judged to be defective after being mounted on the circuit board, the insulating adhesive 107 made of an epoxy series resin which does not adhere to at least one of the electrodes 102 on the circuit board 101 can be softened by heating the defective semiconductor element to about 200 to 230°C, which is a temperature lower than the glass transition point of the insulating adhesive, to reduce the bonding strength. The insulating adhesive 107 can therefore be separated from the circuit board 101 and the semiconductor element 103 can be removed from the circuit board 101 in about 15 seconds. Therefore, the circuit board 101 can be reused, on which an intact semiconductor element 103 is mounted.

Although the above effect is lost, the insulating adhesive 107 may also be applied so as to be applied to the electrode 102 of the circuit board 101, as in a semiconductor device 110 of Fig. 10, or to both the electrode 103a of the semiconductor element 103 and the electrode 102 of the circuit board 101.

The insulating adhesive 107 in the above description is in a liquid state. However, the insulating adhesive can be molded into a pellet or a film, whereby the amount of the insulating adhesive 107 supplied changes less. The insulating adhesive can be supplied at a more constant amount.

At the same time, the insulating adhesive 107, which has been formed into the shape of a pellet or a film, is preferably rectangular or elliptical in a plane with a length-to-width ratio of not less than 1. As will be explained later, a first sealing resin 161 is injected into a gap between the semiconductor element 103 and the circuit board 101 as shown in Fig. 14 after the semiconductor element 103 and the circuit board 101 are fixed to each other by the insulating adhesive 107. When the first sealing resin 161 is injected into the gap between a side end surface and an adjacent portion 206 of the semiconductor element 103 in a direction indicated by arrows 201 in Figs. 21 and 22, air bubbles are generated at a rear end portion 202 of the insulating adhesive 107 in the injection direction of arrow 201, resulting in the formation of a weakened part. Therefore, in order to eliminate the air bubbles, the insulating adhesive 107 is arranged to be aligned with the injection direction in a streamlined form, and further, the insulating adhesive 107 is arranged in a plane so that the ratio of a side size 204 of the adhesive in the injection direction of arrow 201 to a length size 203 of the adhesive in a direction perpendicular to the injection direction is not less than 1.

The above condition of the length and width ratio of not less than 1 can also be applied to a planar shape of the applied insulating adhesive 107 when the insulating adhesive 107 is in a liquid form. Since it is necessary for the pellet or the film-shaped insulating adhesive 107 on the circuit board 101 to contact the counter surfaces 103b of the semiconductor element 103 when the semiconductor element 103 is mounted on the circuit board 101, a height of the pellet or the film-shaped insulating adhesive 107 from the counter surface 101a of the circuit board 101 is set in a manner to enable the contact. For example, the pellet or film is in-plane smaller than a distance between the electrodes 103a of the semiconductor element 103 shown in Fig. 1, and has the height corresponding to a distance between the semiconductor element 103 and the circuit board 101, i.e., 20 to 200 µm and slightly exceeds this distance.

In the case where the pellet or film-shaped insulating adhesive 107 is used, the following effects are obtained. As explained above, when an insulating adhesive 107 in a liquid state is used, an application process for the insulating adhesive 107 and a mounting process for the semiconductor element 103 on the circuit board 101 in steps 2 and 3 in Fig. 20 are carried out separately. In contrast, when the pellet or film-shaped insulating adhesive 107 is used, since the adhesive is solid, the pellet or film-shaped insulating adhesive 107 can be interposed between the circuit board 101 and the semiconductor element 103 while the above-mentioned mounting process is carried out.

Although the insulating adhesive 107 is directly adhered to the mating surface 103b of the semiconductor element 103 in the above description, as will be shown later, an insulating resin 153, for example, an epoxy series resin, may be previously formed on the mating surface 103b of the semiconductor element 103, thereby forming a semiconductor element 150, and thereafter, the semiconductor element 150 may be bonded to the circuit board 101 by the insulating adhesive 107. Specifically, referring to Fig. 8, after the protruding electrodes 104 are bonded to the electrodes 103a of the semiconductor element 103 have been formed, the semiconductor element 103 is placed on a turntable 151. The insulating resin 153 is applied to an approximately central portion on the opposing surface 103b of the semiconductor element 103, and the turntable 151 is rotated in an arrow direction. As a result, as shown in Fig. 9, the insulating resin 153 is dispersed by the centrifugal force so that the opposing surface 103b of the semiconductor element 103 and the electrodes 103a at the periphery of the protruding electrodes 104 are covered with the insulating resin 153. However, front end portions of the protruding electrodes 104 are exposed from the insulating resin 153. The insulating resin 153 is then cured. After setting, the front end portions of the protruding electrodes 104 are pressed against a base material 152 having a flat surface as shown in Figs. 10 and 11, whereby the front end portions of the protruding electrodes 104 are flattened and formed as a bonding surface. Then, the conductive adhesive 106 is applied to the front end portions of the protruding electrodes 104 as explained above as shown in Figs. 12 and 13, and the insulating adhesive 107 is disposed between the semiconductor element 150 and the circuit board 101, thereby bonding the semiconductor element 150 to the circuit board 101. The semiconductor device thus manufactured becomes a semiconductor device 155 shown in Fig. 13.

As explained above, when the insulating resin 153 is formed on the opposing surface 103b of the semiconductor element 103, the insulating resin 153 protects the semiconductor element 103 and further protects the electrodes 103a on the periphery of the protruding electrodes 104, and at the same time makes the semiconductor element excellently resistant to moisture after it is mounted on the circuit board 101 and prevents the electrodes 103a of the semiconductor element 103 from being corroded. According to the semiconductor device 155, the process of injecting and setting the insulating resin into a gap between the circuit board 101 and the semiconductor element 103 can be effectively omitted.

Although the insulating resin 153 may not contain a material such as silicon oxide and the like that controls thermal expansion of the insulating resin 153, if the insulating resin contains this material, it becomes approximately the same as the insulating adhesive 107 in terms of its components, thereby reducing a stress at an interface between the insulating resin 153 and the insulating adhesive 107.

In each of the semiconductor devices 100, 110, 115, 116, 155 described above, the first sealing resin 161 is injected into the gap between the semiconductor element and the circuit board, for example, in a manner as shown in Fig. 14 or in step S of Fig. 20. The injection of the first sealing resin 161 may be omitted in the semiconductor device 155 as explained above. An injection process of the first sealing resin 161 will now be explained by way of example with respect to the semiconductor device 100.

In the injection method, the first sealing resin 161 is injected by a resin injection device 171 from the side end surface of the semiconductor device 100 and one of the portions near the side end surface as indicated by reference numeral 206 in Fig. 14.

Preferably, the inside of a working chamber 173 is reduced to a pressure lower than the atmospheric pressure by an air exhaust device 172 after the semiconductor device 100 is placed in the chamber 173, in which the pressure in the inside thereof can be reduced to a value lower than the atmospheric pressure by the air exhaust device 172. Under the pressure-reduced state, the first sealing resin 161 is applied to the circuit board 101 along four sides of the semiconductor device 100 from the side end surface and the adjacent portion 206 of the semiconductor device 100 by a resin supply device 174 as indicated by the arrows. After the application is completed, the inside of the chamber 173 is returned to the atmospheric pressure. At this time, the gap portion between the semiconductor element 103 and the circuit board 101 is located. which is sealed by the first sealing resin 161 applied along the four sides of the semiconductor device 100 continues in a pressure-reduced state. Due to the pressure difference, the first sealing resin 161 applied along the four sides penetrates into the gap as shown in Fig. 16, thereby filling the gap. The amount of the first sealing resin 161 applied at this time is selected so as to seal the gap between the semiconductor element 103 and the circuit board 101, thereby preventing the intrusion of moisture and corrosion, reducing thermal stress, and ensuring the reliability of the contacted parts.

According to the above-described injection method, the sealing resin can be injected into the gap in a shorter time as compared with the method of applying the insulating sealing resin from the side end part of the semiconductor element 103 and the adjacent portion 206 at atmospheric pressure. Even when the semiconductor element 103 is larger than 15 x 15 mm or even larger, the sealing resin can still be easily injected in a short time.

A heat radiating resin 163 may be provided on the semiconductor device provided with the first sealing resin 161 introduced into the gap as explained above and shown in Fig. 17 to cover the entire surface of the semiconductor device. In this case, the heat radiating resin 163 has a thermal conductivity in the range of 0.2 to 2 W/mk, and preferably 1 W/mk or greater, to effectively radiate the heat generated by the semiconductor device. When aluminum or a similar metallic filler having good thermal conductivity is contained in the first sealing resin 161, the heat radiation efficiency of the semiconductor element 103 can be improved even without using the heat radiating resin 163. When the metallic filler is used, the filler is coated with a resin coating to eliminate the conductivity of the filler.

Instead of the method of injecting the sealing resin, the semiconductor element 103 may be sealed by covering the semiconductor device 100 with, for example, a second sealing resin 162 as shown in Figs. 18 and 19. The second sealing resin 162 is preferably in a film form or in a liquid state. Fig. 18 shows the resin in a liquid state, while Fig. 19 shows the film of the resin. After the semiconductor device 100 is heated in the chamber 173 in the pressure-reduced state, the entire surface of the semiconductor element 103 is covered with the second sealing resin 162. The working chamber 173 is then returned to atmospheric pressure and the second sealing resin 162 is set, whereby the semiconductor device 100 is sealed.

Accordingly, compared with the method of applying and injecting the insulating sealing resin from the side end surface and the adjacent portion 206 of the semiconductor element 103 at atmospheric pressure, the second sealing resin can be applied in a shorter time in the form of a sheet or a sheet, which may be accompanied by an increase in the size of the semiconductor element 103.

Similar to the case where the first sealing resin 161 is used, the heat radiating resin 163 may be additionally provided or the aluminum filler and the like may be contained in the second sealing resin 162.

The first sealing resin 161 and the second sealing resin 162 are preferably made of epoxy or acrylic series, and preferably made of a material containing an epoxy component. The first sealing resin 161 and the second sealing resin 162 may be a thermoplastic resin, which is not limited to a thermosetting resin.

In the semiconductor devices 100, 110, 115, 116, 155 explained above, the protruding electrodes 104 are connected to the electrodes 102 on the circuit board 101 via the conductive adhesive 106. However, the conductive adhesive 106 is not necessarily required. Fig. 23 shows a semiconductor device 211 in which the semiconductor element 103 and the circuit board 101 are bonded to each other only by the insulating adhesive 107 without using the conductive adhesive 106. Since the insulating adhesive 107 has shrinkage properties, the semiconductor element 103 and the circuit board 101 are attracted to each other when bonded via the insulating adhesive 107, and consequently the protruding electrodes 104 abut against the electrodes 102 of the circuit board 101 and are electrically connected thereto.

Even if the semiconductor element 103 and the circuit board 101 are fixed to each other only by the insulating adhesive 107 as explained above, the protruding electrodes 104 are securely connected to the electrodes 102 on the circuit board 101 via the insulating adhesive 107. However, it is better to use the conductive adhesive 106 to further enhance the connection reliability as explained above.

Although the semiconductor element 103 is flat in the above example, the mounting method is not limited to the example and is also applicable to a spherical semiconductor element 213 as shown in Fig. 24. A semiconductor device 215 is obtained with the spherical semiconductor element mounted on the circuit board using the mounting method of the above embodiment.

Although the present invention has been fully explained in connection with the preferred embodiment thereof with reference to the accompanying drawing figures, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Such changes and modifications are considered to be included within the scope of the present invention as defined by the appended claims unless they depart therefrom.

Claims (22)

1. A method for mounting a semiconductor element (103) on a circuit board (101), which includes the following steps: Applying an insulating adhesive (107) having a shrinkage property upon setting to at least each opposing surface (101a, 103b) of the circuit board (101) and the semiconductor element (103) which are opposite to each other; Aligning the circuit board (101) and the semiconductor element (103) so that an electrode (102) on the circuit board (101) corresponds to a protruding electrode (104) on the semiconductor element (103); Connecting the mating surfaces (101a, 103b) of the circuit board (101) and the semiconductor element (103) by means of the insulating adhesive (107); and setting the insulating adhesive (107) so that the electrode (102) on the circuit board (101) and the protruding electrode (104) on the semiconductor element (103) are electrically connected to each other by the shrinkage of the insulating adhesive (107) so that the semiconductor element (103) and the circuit board (101) are fixed in a connected state; characterized in that the method further comprises the step : Before applying the insulating adhesive (107), applying an insulating resin (153) for protecting an electrode (103a) on the semiconductor element (103) to the mating surface (103b) of the semiconductor element (103) except for the portion of the protruding electrode (104) which is connected to the electrode (102) on the circuit board (101), wherein after setting of the insulating resin (153), the insulating adhesive (107) is applied to at least each of the mating surfaces (101a, 103). 2. The method according to claim 1, in which the insulating resin (153) is applied by dropping the insulating resin (153) onto an approximately central portion on the counter surface (103b) of the semiconductor element (103) which is fixed on a turntable (151) and rotating the turntable (151). 3. The method according to claim 1 or 2, which includes, after fixing the circuit board (101) and the semiconductor element (103), injecting a first sealing resin agent (161) into a gap between the circuit board (101) and the semiconductor element (103) from a side end surface and into the adjacent portion (206) of the semiconductor element (103) on the circuit board (101). 4. The method according to claim 3, wherein the insulating adhesive (107) has a pellet shape or a film shape, wherein the first sealing resin agent (161) is injected in one direction into the gap between the circuit board (101) and the semiconductor element (103) from the side end face and into the adjacent portion (206) of the semiconductor element (103) on the circuit board, and where the applied insulating adhesive (107) is rectangular or elliptical in the plane with a size ratio of a longitudinal direction perpendicular to an injection direction of the one direction of the first sealing resin agent (161) to a width direction parallel to the injection direction of not less than 1. 5. The method according to claim 3 or 4, wherein the injecting of the first sealing resin agent (161) into the gap between the circuit board (101) and the semiconductor element (103) includes: Bringing the circuit board (101) and the semiconductor element (103) under a pressure-reduced state below the atmospheric pressure after fixing them; applying the first sealing resin agent (161) to the entire periphery of the semiconductor element (103) along the side end surface and to the adjacent portion (206) of the semiconductor element (103) under the pressure-reduced state to seal the gap; and Returning the circuit board (101) and the semiconductor element (103) to the atmospheric pressure so that the first sealing resin agent (161) applied to the side end surface and the adjacent portion (206) enters the gap due to a pressure difference. 6. A method according to any one of claims 3 to 5, which comprises: Covering the semiconductor element (103) with a heat-emitting resin (163) after the first sealing resin agent (161) has been injected. 7. A method according to claim 1 or 2, which comprises: after fixing the circuit board (101) and the semiconductor element (103), bringing the circuit board (101) and the semiconductor element (103) into a pressure-reduced state lower than the atmospheric pressure; Covering the semiconductor element (103) with a second sealing resin agent (162) under the pressure-reduced state; and Returning the circuit board (101) and the semiconductor element (103) to the atmospheric pressure to seal the semiconductor element (103) on the circuit board (101) by the second sealing resin agent (162). 8. The method according to claim 7, wherein the second sealing resin agent (162) is a resin which has a softening property upon application of heat, which is heated, which is again exposed to atmospheric pressure and which sets when the semiconductor element (103) is covered with the second sealing resin agent (162) under the pressure-reduced state. 9. A method according to claim 7 or 8, which comprises: Coating the second sealing resin agent (162) with a heat-emitting resin (173), after which the semiconductor element (103) is sealed by the second sealing resin agent (162). 10. The method according to any one of claims 7 to 9, wherein the second sealing resin agent (162) has a film form. 11. The method according to any one of claims 7 to 9, wherein the second sealing resin agent (162) is in a liquid state. 12. A method according to any one of claims 1 to 11, which comprises: Providing a conductive adhesive (106) to the protruding electrode (104) on the semiconductor element (103) while applying the insulating adhesive (107) to at least each of the mating surfaces of the circuit board (101) and the semiconductor element (103); Curing the conductive adhesive (106) in parallel with the curing of the insulating adhesive (107) in a parallel curing process so that the electrode (102) on the circuit board (101) continues to be electrically connected to the protruding electrode (104) on the semiconductor element (103). 13. The method of claim 12, wherein in the parallel setting process of the conductive adhesive (106) and the insulating adhesive (107), the insulating adhesive (107) sets and shrinks before the conductive adhesive (106) sets to securely connect the electrode (102) on the circuit board (101) to the protruding electrode (104) on the semiconductor element. 14. The method according to any one of claims 1 to 13, wherein during the setting of the insulating adhesive (107), a setting stress acting on the semiconductor element (103) and the circuit board (101) by the setting and shrinking of the insulating adhesive bers (107) is designed to be 392.3 · 10⁶ to 1176.8 · 10⁶ Pa to protect the semiconductor element (103) and the circuit board (101) from being damaged by the setting and shrinking process of the insulating adhesive (104). 15. The method according to any one of claims 1 to 14, wherein the protruding electrode (104) is formed from Au, Ni, Al, Cu or solder material. 16. Method according to one of claims 1 to 15, in which the insulating adhesive (107) is heat-bonding. 17. The method according to any one of claims 1 to 16, wherein the insulating adhesive (107) is a resin from the epoxy resin series, from the silicone resin series or from a polyimide resin series. 18. The method according to any one of claims 12 to 17, wherein the conductive adhesive (106) is a conductive filler containing silver or gold. 19. The method according to any one of claims 1 to 18, wherein the insulating adhesive (107) is applied in a position so as not to come into contact with the electrode (102) on the circuit board (101) and the protruding electrode (104) on the semiconductor element (103) in the connected state of the semiconductor element (103) and the circuit board (101). 20. A method according to any one of claims 1 to 19, wherein the insulating adhesive (107) is applied to a plurality of points on each of the opposing surfaces (101a, 103b) to reduce the application amount of the insulating adhesive (107) once applied, so that variations in the application amount are reduced. 21. Method according to one of claims 1 to 20, in which the insulating adhesive (107) is cured by a curing oven. 22. A semiconductor device comprising a semiconductor element (103) which has been mounted on a circuit board (101) according to the mounting method according to any of claims 1 to 21.